Gene test could warn of addict tendencies

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A person's susceptibility to developing depression, anxiety and alcohol and drug addiction could all be just a DNA test away.

The issue is particularly on the mind of Victoria University researcher Bridget Brox, who is studying a gene known as 5-HTT.

Having a different form of this DNA sequence could have astoundingly different consequences on a person's potential to develop mood and emotional disorders and addiction.

The gene has two forms, known as "short" and "long". In New Zealand, about 45 per cent of the population has at least one of the short forms, making them more susceptible to mood and emotional issues, studies suggest.

After working on the gene, Brox planned to be tested to see what versions she had.

"I'm just curious. I don't use hard drugs but if I knew I had incredibly high risk that might even inform my decisions about alcohol," Brox said.

"I think it would be brilliant for individuals to have that information, for personal use only . . . Drug use is such a burden and a problem, if we can get individual information, prior to, I think that would be a tremendous step."

While science has not yet cracked the full code, 5-HTT is one of several genes that can affect how susceptible people are to becoming addicted to hard drugs, Brox said.

Brox has studied rats with the short and long version of the gene and how they behave when they get access to ecstasy. The rats with the short genes take significantly more of the drug than those with the long version.

"You're more sensitive [to the drug], re-enforcing drug-taking behaviour, making it more likely to happen again.

"But it becomes so incredibly complex in humans because I might have extremely high risk, but I may never try anything. You can't become addicted if you're not taking in the substances."

National Addiction Centre director Doug Sellman believed people might make more sensible choices if they knew their "addictive potential".

However, this could already be identified by looking at their family history, personality type and susceptibility to withdrawal, including hangovers in the case of alcohol, he said. Testing the 300 to 400 interacting genes relating to addiction might only cause unnecessary anxiety.

"Depending on where you sit on the continuum of vulnerability will determine how hard you have to work at it to become addicted. We all can become addicted if we try hard enough."

For US$99 (NZ$113) - or US$173.95 (NZ$199) if international - customers could be screened for genetic risks of developing 120 diseases, including cardiac disease, cancers, and even brain aneurisms. Each person would be classified as "elevated risk", "typical risk" or "decreased risk" for each health issue.

The FDA was concerned that a false positive could lead people to having unnecessary procedures.

The company stopped selling its health screening tests last November, though it is working to have such tests approved by the FDA. Chief regulatory officer Kathy Hibbs said 23andme saw its work as "empowering individuals with their genetic information".